Auto exposure controlling device and method

ABSTRACT

An automatic exposure (AE) controlling device and method are provided. According to the method, an electric shutter (ES) value and an analog gain control (AGC) value can be calculated through a proportional integral control method according to a brightness value of an inputted image frame. Then, AE compensation on a present image frame can be performed using the calculated ES value and AGC value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/861,818, filed Sep. 26, 2007, now U.S. Pat. No. 7,859,577, issuedDec. 28, 2010, which claims the benefit under 35 U.S.C. §119 of KoreanPatent Application No. 10-2006-0093579, filed Sep. 26, 2006, which ishereby incorporated by reference in its entirety.

BACKGROUND

High-level automatic control technology is often applied to industrialrobots and machine tools to improve their performance. Examples ofautomatic control technology include an open loop system and a closedloop system.

In an open loop system, such as a non-feedback system, a sequencecontrol is typically used. This non-feedback system is not often used,though. A closed loop system, such as a feedback system, can beexpensive, but is often used in industries due to the ability toaccurately compensate for a present value.

A feedback system generally includes a proportional controller, anintegral controller, a proportional integral controller, a proportionalderivative integral controller, a fuzzy controller, and a fuzzyproportional derivative integral controller. A controller can be usedaccording to system properties, depending on which controller isappropriate. A proportional integral controller and a proportionalderivative controller are most often used.

A proportional integral control method is typically used in anon-motorized system. This method has advantages in improving a responsetime of the system, preventing excessive overshoot, and enhancingstability.

In order to control automatic exposure (AE) of a camera module, a deviceincludes digital control technology to maintain the brightness of animage in the optimized state regardless of the illumination of a lightsource.

An AE controlling function automatically controls the brightness of animage by considering the light intensity of a subject and itssurroundings, and the reflectivity of the subject.

For a digital cameral module, an AE algorithm is often implemented in animage signal processor (ISP) to perform the AE controlling function. TheAE controlling function adjusts the brightness level of the subject foreach input image frame in correspondence to the illumination changearound the subject and the brightness of the subject.

A related art AE algorithm processes feedback signal data before an AEcompensation control in an aspect of a signal process. Therefore, thisis limited to only compensating for a difference of a target brightnessvalue and a present brightness value.

The related art AE algorithm writes an electrical shutter (ES) value andan automatic gain control (AGC) value with respect to the variousbrightness values in a database through a great number of experiments.Then, when performing AE compensation, the ES value and the AGC valuethat correspond to the processed present brightness data are utilizedthrough image signal processing.

However, according to this related art method, memory usage in the ISPincreases. Also, it takes a relatively long time to develop variousalgorithms, and malfunctions often occur in unexpected environments.

Furthermore, AE accuracy is limited because the time for processing animage signal is not taken into consideration.

Thus, there exists a need in the art for an improved device and methodfor controlling AE.

BRIEF SUMMARY

Embodiments of the present invention provide a device and a method forcontrolling automatic exposure (AE) by using a proportional integralcontrol method.

Embodiments of the present invention also provide a device and a methodfor controlling AE by correcting hunting due to feedback delay.

In an embodiment, an auto exposure controlling method can include:calculating an electric shutter (ES) value through a proportionalintegral control method according to a brightness value of an inputtedimage frame; calculating an analog gain control (AGC) value through theproportional integral control method according to a brightness value ofan inputted image frame; and performing AE compensation on a presentimage frame using the calculated ES value and the calculated AGC value.

In an embodiment, an auto exposure control device can include: an imagesensor for converting light intensity of an incident image into ananalog image signal; an analog front end (AFE) for receiving the analogimage signal to convert the analog image signal into a digital imagesignal, and for controlling operations of the image sensor; and acontroller for calculating an ES value and an AGC value by using aproportional integral control method according to a brightness value ofan inputted image signal from the AFE, and for controlling an exposuretime of the image sensor and an analog gain of the AFE.

The details of one or more embodiments are set forth in the accompanyingdrawings and the detailed description below. Other features will beapparent to one skilled in the art from the detailed description, thedrawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an AE controlling device.

FIGS. 2 and 3 are flowcharts of methods for adjusting an ES value and anAGC value according to an embodiment of the present invention.

FIG. 4 is a view of feedback delay according to an embodiment of thepresent invention.

FIG. 5 is a graph illustrating a brightness value of an image frame withrespect to an AGC value and an ES value.

DETAILED DESCRIPTION

Referring to FIG. 1, an automatic exposure (AE) controlling device caninclude a lens 10 through which an image can enter, an image sensor 20which can convert light incident through the lens 10 into an analogimage signal (such as an electrical signal), an analog front end (AFE)30 which can receive the analog image signal from the image sensor 20and can convert it into a digital image signal, and a controller 40which can process the digital image signal from the AFE 30 foroutputting and controlling the AFE 30. The AFE 30 can also be used incontrolling the image sensor 20.

The image sensor 20 can be, for example, a complementary metal oxidesemiconductor (CMOS) image sensor or a charge coupled device (CCD) imagesensor.

The AFE 30 can include, for example, an analog to digital converter(ADC). The AFE 30 can convert the analog image signal outputted from theimage sensor 20 into a digital image signal and can provide it to thecontroller 40.

Additionally, the AFE 30 can generate various clocks, for example,HSync, YSync, and timing generator (TG), to drive the image sensor 20.

The AFE 30 can adjust an analog gain of the analog image signal throughcontrol of the controller 40.

The controller 40 can include, for example, an image signal processor(ISP) and a micro controller unit (MCU).

The controller 40 can convert digital data, which can be inputted fromthe AFE 30 through the ISP, into YCrCb (luminance and chrominance) dataand can detect the brightness of the inputted image signal.Additionally, the controller 40 can perform digital gain control withrespect to the image signal through the ISP.

The controller 40 can perform automatic exposure (AE), auto whitebalance (AWB), and auto focus (AF) through the MCU. The controller 40can also output automatic exposure (AE), auto white balance (AWB), andauto focus (AF) as image data.

The controller 40 can control exposure time of the image sensor 20 andanalog gain of the AFE 30 to compensate image brightness for outputting.

The controller 40 can calculate an electric shutter (ES) value forcontrolling an exposure delay time of the image sensor 20 and an analoggain control (AGC) value for controlling analog gain of the AFE 30. Thecontroller can calculate an ES value and an AGC value through, forexample, a proportional integral method to perform an AE control.

When performing the AE control, the ES value and the AGC value can beapplied in consideration of a noise component's influence.

That is, if image brightness were to be increased by reducing the ESvalue, the noise component may not change, but if image brightness wereto be increased by enhancing the AGC value, the noise component may beamplified, such that image quality can be deteriorated.

Accordingly, in an embodiment, when performing the AE control toincrease the image brightness, the ES value can be adjusted first beforeadjusting the AGC value. When performing the AE control to decrease theimage brightness, the AGC value can be adjusted first before adjustingthe ES value.

The ES value can indicate how long exposure time is delayed, duringwhich electric charges can be accumulated in a pixel of the image sensor20. Thus, as the ES value increases, time for accumulating the electriccharges can decrease. As a result, the brightness value of an image candecrease.

For example, if the ES value is 100, the image sensor 20 can count from1 to 100 and can then start accumulating electric charges. Accordingly,as the ES value increases, time for accumulating electric charges candecrease.

The AGC value can indicate analog gain of an image signal, and as theAGC value increases, the brightness value can increase.

The ES value and the AGC value can be written in a resister of the AFE30, and the exposure delay time and the analog gain can be determinedaccording to the values written in the register.

FIGS. 2 and 3 are flowcharts of methods for adjusting an ES value and anAGC value according to an embodiment of the present invention.

A noise component can often be very important in determining the qualityof an image. Thus, when performing an AE control to increase imagebrightness, the ES value, which can have less effect on the noisecomponent, can be adjusted first, and the AGC value can be adjusted onlyif the ES value is out of range.

Referring to FIG. 2, it can first be determined whether the ES value inthe register of the AFE 30 is larger than the adjustable minimum value,ES_Min, and smaller than the adjustable maximum value, ES_Max, inoperation S210.

If the ES value is within the range, ES_Min<ES<ES_Max, the ES value forobtaining desirable image brightness can be calculated through aproportional integral control method in operation S220.

If the desirable image brightness can be obtained by only adjusting theES value, the ES value can be selected as a value larger than ES_Min andless than ES_Max, and then the AE control can be performed using the ESvalue and the AGC value stored in the AFE 30 in operations S230 andS240.

If the desirable image brightness cannot be obtained by only adjustingthe ES value, the ES value can be calculated as ES_Min, and then storedin the register of the AFE 30 in operations S220, S230, and S240.

It can then be determined again whether the ES value is within therange, ES_Min<ES<ES_Max, in operation S210.

Since in this case the ES value is stored as ES_Min (S250), it can bedetermined whether the AGC value stored in the register of the AFE 30 islarger than the adjustable minimum value, AGC_Min, and less than theadjustable maximum value, AGC_Max, in operation S260.

If the AGC value is within the range, AGC_Min<AGC<AGC_Max, the AGC valuefor obtaining desirable image brightness can be calculated through aproportional integral control method in operation S270.

If the desirable image brightness can be obtained by adjusting the AGCvalue in this way, the AGC value can be selected as a value larger thanAGC_Min and less than AGC_Max, and then the AE control can be performedusing the ES value and the AGC value stored in the AFE 30 in operationsS230 and S240.

If the desirable image brightness cannot be obtained by adjusting theAGC value in this way, the AGC value can be calculated as the AGC_Maxvalue, and then stored in the register of the AFE 30 in operations S270,S230, and S240.

In an embodiment, when performing the AE control to increase imagebrightness, the ES value can be adjusted first to compensate imagebrightness. When the desirable image brightness cannot be obtained byadjusting only the ES value, the AGC value can be adjusted.

FIG. 3 is a flowchart of an AE control that can reduce image brightness.

Referring to FIG. 3, it can be determined whether the AGC value storedin the register of the AFE 30 is larger than the adjustable minimumvalue, AGC_Min, and less than the adjustable maximum, AGC_Max, inoperation S310.

If the AGC value is within the range, AGC_Min<AGC<AGC_Max, the AGC valuefor obtaining desirable image brightness can be calculated through aproportional integral control method in operation S320.

If the desirable image brightness can be obtained by only adjusting theAGC value, the AGC value can be selected as a value larger than AGC_Minand less than AGC_Max, and the AE control can be performed using the AGCvalue and the ES value stored in the AFE 30 in operations S330 and S340.

If the desirable image brightness cannot be obtained by only adjustingthe AGC value, the AGC value can be calculated as the AGC_Min value, andthen stored in the register of the AFE 30 in operations S320, S330, andS340.

It can then be determined again whether the AGC value is within therange, AGC_Min<AGC<AGC_Max, in operation S310.

Since in this case the AGC value is stored as AGC_Min, it can bedetermined whether the ES value stored in the register of the currentAFE 30 is larger than the adjustable minimum value, ES_Min, and lessthan the adjustable maximum value, ES_Max, in operations S350 and S360.

If the ES value is within the range, ES_Min<ES<ES_Max, the ES value forobtaining desirable image brightness can be calculated through aproportional integral control method in operation S370.

If the desirable image brightness can be obtained by adjusting the ESvalue in this way, the ES value can be selected as a value larger thanES_Min and less than ES_Max, and the AE control can be performed usingthe ES value and the AGC value stored in the AFE 30 in operations S330and S340.

If the desirable image brightness cannot be obtained by adjusting the ESvalue in this way, the ES value can be calculated as the ES_Max value,and then stored in the register of the AFE 30 in operations S370, S330,and S340.

In an embodiment, when performing the AE control to reduce imagebrightness, the AGC value can be adjusted first to compensate the imagebrightness. If the desirable image brightness cannot be obtained by onlyadjusting the AGC value, the ES value can be adjusted.

According to an AE control method, when adjusting the ES value and theAGC value, although the image brightness value can be compensated to thetarget value, it may be uncomfortable to a viewer if the imagebrightness value is suddenly changed.

Accordingly, while performing AE compensation, the image brightnessvalue should be smoothly changed. To accomplish a smooth transition, amanipulated variable of the ES value and a manipulated variable of theAGC value can be calculated through a proportional integral controlmethod.

The manipulated variable of the ES value and the manipulated variable ofthe AGC value can be calculated using Equation 1 below.MV_(n)=MV_(n-1)+ΔMV_(n),  (1)where MV_(n), and MV_(n-1) represent the present manipulated variableand the previous iteration manipulated variable, respectively, andΔMV_(n) represents a derivative of the present manipulated variable.

Each manipulated variable can be calculated through Equation 1.

Here, ΔMV, can be expressed by Equation 2 below.ΔMV_(n) =K _(p)(e _(n) −e _(n-1))+K _(i) e _(n),  (2)

where K_(p) and K_(i) represent a proportional control constant and anintegral control constant, respectively, e_(n) represents a deviation ofthe present manipulated variable, and e_(n-1) represents a deviation ofthe previous iteration manipulated variable.

In an embodiment, according to the results of a test using Equation 2,the expression can smoothly approach a target value without hunting atK_(p)=0.47 and K_(i)=0.55.

For example, it can be important for an AE algorithm of a mobile camerasystem to operate at a high speed, but it can be more important for itto converge with no hunting.

However, because the feedback of an image frame brightness value can bedelayed even with the proportional integral control through the aboveEquations 1 and 2, hunting may occur.

FIG. 4 is a view of feedback delay according to an embodiment of thepresent invention.

Referring to FIG. 4, FD, CV, and F represent a feedback value, a controlvalue, and an image frame, respectively. The control value (CV) can be,for example, the ES value or the AGC value.

For example, a value CV_(n-1) can be written into a register when aframe F_(n-1) is finished, and the value CV_(n-1) can be applied to aframe F_(n-2). The value CV_(n-1) applied to the frame F_(n-2) can reada value FD_(n-2) when the frame F_(n-1) progresses due to an operationof calculating.

In a typical ISP, if there is a difference after comparing the frameF_(n-1) with a target value, it can compensate the ES value and the AGCvalue for the difference. As a result, brightness value change of theframe can be the result of the feedback whose brightness value is avalue from two frames previous, not the last frame. Due to thisproperty, since the value of two frames previous can become the feedbackduring the entire AE period, hunting may occur.

According to an embodiment of the present invention, the AE compensationcan be performed by considering a delay variable for compensation in thefeedback of the image frame brightness value.

The frame delay variable can be reflected through Equation 3.

$\begin{matrix}{{{CFD}_{n} = {{FD}_{n} + {\sum\limits_{k = 0}^{1}\;{UD}_{n - k}} - {\sum\limits_{k = 0}^{1}{DD}_{n - k}}}},} & (3)\end{matrix}$

where CFD and FD represent the final value of feedback and presentfeedback, respectively, and UD and DD represent a brightness changevalue when a frame brightness value increases, and a brightness changevalue when a frame brightness value decreases, respectively.

Through Equation 3, the final value of feedback (CFD) can be the resultof when the brightness change value (UD or DD) of the two frames isreflected on the present feedback (FD).

If the brightness value increases, UD data can be reflected andotherwise, DD data can be reflected. Here, UD and DD can be obtained byexperiment using expected values of the AGC value and the ES value.Values of UD and DD can be obtained, for example, by the methoddescribed with reference to FIG. 5.

FIG. 5 is a graph illustrating a brightness value of an image frame withrespect to an AGC value and an ES value. Line (1) represents when AGC isabout 14.15 dB, line (2) represents when AGC is about 15.9 dB, and line(3) represents when AGC is about 17.65 dB.

Referring to FIG. 5, the brightness change value can be obtained usingthe AGC value and the ES value.

For example, the brightness value is about 210 when the AGC value isabout 14.15 dB and the ES value is about 406 in a first frame. Thebrightness value is about 240 when the AGC value is about 15.9 dB andthe ES value is about 406 in a second frame. The brightness value isabout 270 when the AGC value is about 17.65 dB and the ES value is about406 in a third frame. Here, since there is an increase of about 30 inthe brightness value between the first frame and the second frame,UD_(n-1) is 30. Since there is an increase of about 30 in the brightnessvalue between the second frame and the third frame, UD, is 30. That is,if the present feedback value is 300, the final value CFD is 360(=300+30+30).

In an embodiment, to apply Equation 3 to Equation 2, Equations 4 and 5can be used, as shown below.e _(n) =T−CFD _(n),  (4)where T represents a target brightness value.e _(n-1) =T−CFD _(n-1)  (5)

Equations 4 and 5 can become Equations 6 and 7 as follows.

$\begin{matrix}{e_{n} = {T - {FD}_{n} + {\sum\limits_{k = 0}^{1}\;{UD}_{n - k}} - {\sum\limits_{k = 0}^{1}{DD}_{n - k}}}} & (6) \\{{e_{n} - 1} = {T - {FD}_{n - 1} + {\sum\limits_{k = 1}^{2}\;{UD}_{n - k}} - {\sum\limits_{k = 1}^{2}{DD}_{n - k}}}} & (7)\end{matrix}$

The deviation e_(n)−e_(n-1) of a proportional term can be obtained usinge_(n) and e_(n-1) through Equation 8 below.

$\begin{matrix}\begin{matrix}{{e_{n} - e_{n - 1}} = {T - {CFD}_{n} - \left( {T - {CFD}_{n - 1}} \right)}} \\{= {{CFD}_{n - 1} - {CFD}_{n}}} \\{= {{FD}_{n - 1} - {FD}_{n} - \left( {{UD}_{n} - {UD}_{n - 2}} \right) + \left( {{DD}_{n} - {DD}_{n - 2}} \right)}}\end{matrix} & (8)\end{matrix}$

If applying e_(n) and e_(n)−e_(n-1) into Equation 2, it becomes Equation9 below.

$\begin{matrix}{{\Delta\;{MV}_{n}} = {{K_{p}\left\lbrack {= {{FD}_{n - 1} - {FD}_{n} - \left( {{UD}_{n} - {UD}_{n - 2}} \right) + \left( {{DD}_{n} - {DD}_{n - 2}} \right)}} \right\rbrack} + {K_{i}\left\lbrack {T - \left( {{FD}_{n} + {\sum\limits_{k = 0}^{1}{UD}_{n - k}} - {\sum\limits_{k = 0}^{1}{DD}_{n - k}}} \right)} \right\rbrack}}} & (9)\end{matrix}$

Equation 9 is the final equation of a proportional integral controlmethod according to an embodiment of the present invention whenconsidering the frame delay variable.

When applying ΔMV, in Equation 9 to Equation 1, the manipulatedvariables of the ES value and the AGC value can be calculated. Also theAE compensation of a camera module can be performed according to thecalculated ES value and AGC value.

According to embodiments of the present invention, an AE controllingdevice and method can apply the proportional integral control method tothe AE compensation in the camera module. The delay of the image framefeedback due to the image signal process can be considered. As a result,stability and speed can be enhanced.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. An automatic exposure (AE) controlling method,comprising: calculating, via a controller, an electric shutter (ES)value through a proportional integral control method; calculating, viathe controller, an analog gain control (AGC) value through theproportional integral control method; and performing, via thecontroller, AE compensation on a present image frame using thecalculated ES value and the calculated AGC value, wherein calculatingthe ES value and calculating the AGC value comprises using a feedbackdelay variable for compensation in feedback of a brightness value of animage frame, and wherein the feedback delay variable comprises abrightness change value including brightness chance expected value of animage frame between an image frame with an input brightness value andthe present image frame, and a brightness change expected value of thepresent image frame.
 2. The method according to claim 1, wherein forincreasing a brightness value of a present image frame, performing theAE compensation comprises: applying the calculated ES value for thepresent image frame; and wherein when the calculated ES value for thepresent image frame provides a desirable image brightness for the AEcompensation, the calculated AGC value for a previous image frame isused with the calculated ES value for the present image frame to performthe AE compensation, and wherein when the AE compensation required toprovide the desirable image brightness exceeds an adjusting range of thecalculated ES value, both the calculated ES value for the present imageframe and the calculated AGC value for the present image frame areapplied to perform the AE compensation.
 3. The method according to claim1, wherein for decreasing a brightness value of a present image frame,performing the AE compensation comprises: applying the calculated AGCvalue for the present image frame; and wherein when the calculated AGCvalue for the present image frame provides a desirable image brightnessfor the AE compensation, the calculated ES value for a previous imageframe is used with the calculated AGC value for the present image frameto perform the AE compensation, and wherein when the AE compensationrequired to provide the desirable image brightness exceeds an adjustingrange of the calculated AGC value, both the calculated ES value for thepresent image frame and the calculated AGC value for the present imageframe are applied to perform the AE compensation.
 4. The methodaccording to claim 1, wherein the feedback delay variable comprises abrightness change value between the brightness value of the image frameand a present brightness value of the present image frame.
 5. The methodaccording to claim 4, wherein the brightness change value comprises abrightness change expected value of an intermediate image frame betweenthe image frame with the brightness value and the present image frame,and a brightness change expected value of the present image frame. 6.The method according to claim 4, wherein the image frame with thebrightness value is two frames before the present image frame.
 7. Themethod according to claim 1, wherein the proportional integral controlmethod comprises using manipulated ES value and AGC value variables, andwherein each manipulated ES value and AGC value variable is calculatedusing the following equation:MV_(n)=MV_(n-1)+ΔMV_(n), where MV_(n) represents a present value of themanipulated variable, MV_(n-1) represents a previous iteration value ofthe manipulated variable, and ΔMV_(n) represents a derivative of thepresent value of the manipulated variable.
 8. The method according toclaim 7, whereinΔMV_(n) =K _(p)(e _(n) −e _(n-1))+K _(i) e _(n), where K_(p) representsa proportional control constant, K_(i) represents an integral controlconstant, e_(n) represents a deviation of the present value of themanipulated variable, and e_(n-1) represents a deviation of the previousiteration value of the manipulated variable.
 9. The method according toclaim 8, wherein a feedback delay variable is calculated using thefollowing equation:${{CFD}_{n} = {{FD}_{n} + {\sum\limits_{k = 0}^{1}{UD}_{n - k}} - {\sum\limits_{k = 0}^{1}{DD}_{n - k}}}},$where CFD represents a final feedback value, FD represents a presentfeedback value, UD represents a brightness change value when a framebrightness value increases, and DD represents a brightness change valuewhen a frame brightness value decreases.
 10. The method according toclaim 9, wherein  e_(n) = T − CFD_(n),  e_(n − 1) = T − CFD_(n − 1),  and${\Delta\;{MV}_{n}} = {{K_{p}\left\lbrack {= {{FD}_{n - 1} - {FD}_{n} - \left( {{UD}_{n} - {UD}_{n - 2}} \right) + \left( {{DD}_{n} - {DD}_{n - 2}} \right)}} \right\rbrack} + {K_{i}\left\lbrack {T - {FD}_{n} + {\sum\limits_{k = 0}^{1}{UD}_{n - k}} - {\sum\limits_{k = 0}^{1}{DD}_{n - k}}} \right\rbrack}}$where T represents a target brightness value, e_(n) represents adeviation of the present value of the manipulated variable, e_(n-1)represents the deviation of the previous iteration value of themanipulated variable, K_(p) represents the proportional controlconstant, and K_(i) represents the integral control constant.
 11. Anautomatic exposure (AE) control device, comprising: an image sensor toconvert light intensity of an incident image into an analog imagesignal; an analog front end (AFE) capable of receiving the analog imagesignal to convert the analog image signal into a digital image signal,and controlling operations of the image sensor; and a controller capableof calculating an electric shutter (ES) value and an analog gain control(AGC) value using a proportional integral control method according to abrightness value of the digital image signal from the AFE, and capableof controlling an exposure time of the image sensor and an analog gainof the AFE using the calculated ES value and the calculated AGC value,wherein the ES value and the AGC value are calculated using a feedbackdelay variable for compensation in feedback of an inputted brightnessvalue of an inputted image frame, and wherein the feedback delayvariable comprises a brightness change value including a brightness thanexpected value of an image frame between an image frame with an inputbrightness value and the present image frame, and a brightness changeexpected value of the present image frame.
 12. The device according toclaim 11, wherein the controller is capable of writing the calculated ESvalue and the calculated AGC value in a register of the AFE.
 13. Thedevice according to claim 11, wherein for increasing a brightness valueof a present image frame, the controller is capable of controlling theexposure time of the image sensor and the analog gain of the AFE byperforming automatic exposure compensation, wherein the automaticexposure compensation comprises: applying the calculated ES value forthe present image frame; and wherein when the calculated ES value forthe present image frame provides a desirable image brightness for the AEcompensation, the calculated AGC value for a previous image frame isused with the calculated ES value for the present image frame to performthe AE compensation, and wherein when the AE compensation required toprovide the desirable image brightness exceeds an adjusting range of thecalculated ES value, both the calculated ES value for the present imageframe and the calculated AGC value for the present image frame areapplied to perform the AE compensation.
 14. The device according toclaim 11, wherein for decreasing a brightness value of a present imageframe, the controller is capable of controlling the exposure time of theimage sensor and the analog gain of the AFE by performing automaticexposure compensation, wherein the automatic exposure compensationcomprises: applying the calculated AGC value for the present imageframe; and wherein when the calculated AGC value for the present imageframe provides a desirable image brightness for the AE compensation, thecalculated ES value for a previous image frame is used with thecalculated AGC value for the present image frame to perform the AEcompensation, and wherein when the AE compensation required to providethe desirable image brightness exceeds an adjusting range of thecalculated AGC value, both the calculated ES value for the present imageframe and the calculated AGC value for the present image frame areapplied to perform the AE compensation.
 15. The device according toclaim 11, wherein the feedback delay variable comprises a brightnesschange value between the inputted brightness value of the inputted imageframe and a present inputted brightness value of a present image frame.16. The device according to claim 15, wherein the brightness changevalue comprises a brightness change expected value of an intermediateinputted image frame between the inputted image frame with the inputtedbrightness value and the present inputted image frame, and a brightnesschange expected value of the present inputted image frame.
 17. Thedevice according to claim 15, wherein the image frame with the inputtedbrightness value is two frames before the present inputted image frame.18. An automatic exposure (AE) controlling method, comprising:calculating, via a controller, an electric shutter (ES) value through aproportional integral control method; calculating, via the controller,an analog gain control (AGC) value through the proportional integralcontrol method; and performing, via the controller, AE compensation on apresent image frame using the calculated ES value and the calculated AGCvalue, wherein calculating the ES value and calculating the AGC valuecomprises using a feedback delay variable for compensation in feedbackof a brightness value of an image frame, and wherein the proportionalintegral control method comprises using manipulated ES value and AGCvalue variables, and wherein each manipulated ES value and AGC valuevariable is calculated using the following equation:MV_(n)=MV_(n-1)+ΔMV_(n), where MV_(n) represents a present value of themanipulated variable, MV_(n-1) represents a previous iteration value ofthe manipulated variable, and ΔMV_(n) represents a derivative of thepresent value of the manipulated variable.
 19. The method according toclaim 18, wherein the feedback delay variable comprises a brightnesschange value between the brightness value of the image frame and apresent brightness value of the present image frame.
 20. The methodaccording to claim 19, wherein the brightness change value comprises abrightness change expected value of an intermediate image frame betweenthe image frame with the brightness value and the present image frame,and a brightness change expected value of the present image frame. 21.The method according to claim 19, wherein the image frame with thebrightness value is two frames before the present image frame.
 22. Themethod according to claim 18, whereinΔMV_(n) =K _(p)(e _(n) −e _(n-1))+K _(i) e _(n), where K_(p) representsa proportional control constant, K_(i) represents an integral controlconstant, e_(n) represents a deviation of the present value of themanipulated variable, and e_(n-1) represents a deviation of the previousiteration value of the manipulated variable.
 23. The method according toclaim 22, wherein a feedback delay variable is calculated using thefollowing equation:${{CFD}_{n} = {{FD}_{n} + {\sum\limits_{k = 0}^{1}{UD}_{n - k}} - {\sum\limits_{k = 0}^{1}{DD}_{n - k}}}},$where CFD represents a final feedback value, FD represents a presentfeedback value, UD represents a brightness change value when a framebrightness value increases, and DD represents a brightness change valuewhen a frame brightness value decreases.
 24. The method according toclaim 23, wherein  e_(n) = T − CFD_(n),  e_(n − 1) = T − CFD_(n − 1),  and${\Delta\;{MV}_{n}} = {{K_{p}\left\lbrack {= {{FD}_{n - 1} - {FD}_{n} - \left( {{UD}_{n} - {UD}_{n - 2}} \right) + \left( {{DD}_{n} - {DD}_{n - 2}} \right)}} \right\rbrack} + {K_{i}\left\lbrack {T - {FD}_{n} + {\sum\limits_{k = 0}^{1}{UD}_{n - k}} - {\sum\limits_{k = 0}^{1}{DD}_{n - k}}} \right\rbrack}}$where T represents a target brightness value, e_(n) represents adeviation of the present value of the manipulated variable, e_(n-1)represents the deviation of the previous iteration value of themanipulated variable, K_(p) represents the proportional controlconstant, and K_(i) represents the integral control constant.